Spark plug



Sept. 28, 1937. .1. H. DOAK 2,094,447

SPARK PLUG Original Filed April 26, 1935 Zsnnentor r g ,3 v

Cttomeg Patented Sept. 28, 1937 UNITED STATES SPARK PLUG John H. Doak, Portland, reg., assignor of onefourth to Henrietta S. Rupp and one-fourth to Anna Whitehead, both of Oakland, Calif Application April 26, 1935," Serial No. 18,335

Renewed March 1, 1937 i Claims. (01. 123-169) This invention relates to certain improvements to be provided in spark plugs that are employed in connection with internal combustion engines.

It is one of the objects of the invention to 5 provide a chamber in the core of the plug, this chamber serving as a spark gap to intensify the spark. The object of the invention also contemplates placing within the chamber, between the anode and cathode of the gap, an electrode which serves as a bridge, between the anode and cathode, and as a diffusing member for a vaporous conducting medium. The object of the invention is also to employ mercury in the chamber of the core, employing its changeability from its natural state to a vaporous state to provide a conducting medium, when in a vaporous state, for electrical discharges between anode and cathode.

The further object of the invention is to provide in the core transparent portions whereby the electrical discharges within the chamber may be observed.

The object of the invention is to provide a hot spark during the interval the engine is being started and warmed up, and a cool intense spark thereafter, thus providing for easy starting of the engine in one instance, and steady operation, avoidance of burned points, and the like, in the other instance.

These objects and others will be readily un-.

derstood upon reading the following description, aided by the accompanying drawing, wherein- Figure 1 is a side sectional View of a core of a spark plug, this invention, showing its internal chamber.

Figure 2 is. a side elevation and partial section.

Figure 3 is the cross section indicated by section lines 33 in Figure 2.

In the drawing like numerals indicate like parts throughout the several views. The numeral I indicates an insulated core having an outer form adapting it to be employed in connection with the usual bushings employed for securing spark plugs to internal combustion engines. This core has a substantial internal chamber 2 running lengthwise interiorly thereof. The upper end of the core has a cap 3 having the usual threaded r means 4 for connection with a source of electric energy. The core is made of suitable insulative material, such as porcelain. Projecting from cap 3 through the head of the core and slightly into the upper end of the chamber 2 is an electrode 5, or anode. In the bottom of the chamber is a metal plate 6 which serves as a cathode in conjunction with the member 5. Tothis is attached a pin or wire I extending through the lower end of the core and terminating in a spark point 8 which serves the purpose well known to the art. 5

In conjunction with the elements just described there is employed within the chamber a bridging electrode and difiusing member 9. This memher is spaced between the upper and lower ends of the chamber, occupying a more or less transl0 verse plane, and is supported by having its edges seated in the walls of the member i defining the chamber. Member 9 is preferably perforate and preferably for the purpose is a screen formed of copper. The two layers of screen material em- 15 ployed are spaced from each other at their centers, though touching at their edges.

In order to observe the interior of the inside of chamber 2 so that electrical reaction may be observed, the sides of the core are provided with 20 transparent portions it) formed of suitable material, such as glass. 1

In operation the core is attached to aninternal combustion engine, suitable bushings being employed for this purpose, the member 4 being 25 connected to the ignition system thereof. Ordinarily, in ignition systems, when there is a gap existing between the, distributor or supply means and the discharge or tips of the plugs, there is a building up or intensifying of the electric cur- Q rent which has a tendency over prolonged periods of time to heat the plugs to an extreme, ex-- tent, burning the tips of the plugs, and otherwise producing other than desired results. This condition is usually spoken of as a hot spark, 35 while the reverse thereto is spoken of as a cold spar In cold weather, for initial starting and warming of gas motors, the hot spark is an aid. However for prolonged driving of the motor, the hot spark has its bad effects such as burning 40 out the points of the plugs. On the other hand for prolonged driving of the motor the cold spark does not burn the points of the plugs, provides satisfactory combustion and is more dependable.

In the present invention the plug initially oper- 45 ates to provide a hot spark. This is occasioned by the spacing between the anode 5 and cathode 6. The spark in order to ground from tip 8 must cross the gap formed by the chamber 2. As is well known there is a momentary building up of the voltage on the anode 5 after which the electric charge jumps the gap toward the oathode 6. However in the present invention the charge Jumps first to the intermediate electrode 55 9 and thence to the cathode 6.

ent instance it is proposed to employ a substance which will provide a medium for the passage of electric charges or current. This medium is mercury, a modicum thereof being indicated by the numeral l I. In the initial starting of the gas engine the mercury rests uponthe cathode 6 and the spark jumps from the anode thereto. After an interval the intensity of the spark causes the mercury to spread upon the walls of the chamber 2 and to become transformed into mercury vapor, as indicated by numeral i2, which is transfused by the screen 9. Now the mercury on the walls of the chamber and the vapor ofier a path for the travel of the electric charge thus decreasing very materially its heat producing qualities, the result being a cold spark for ordinary running conditions. After the mercury has been reduced to the condition aforesaid the screen 9 aids very materially in its conductivity.

The window I0 provides means for observing the efliciency of the spark. The windows also serve to tell whether the plug is operating normally or not. In the event that the plug is not working normally or at all there will be a weak spark within the chamber or none .at all as the case may be.

While a specific form of the improvement has been described and illustrated herein, it is desired to be understood that the same may be varied, within the scope of the appended claims, without departing from the spirit of the invention.

What is claimed is- 1. In a spark plug for internal combustion engines, an insulated core provided with a longitudinal chamber, an anode at one end of the changeable in the presence of electric discharges to a vaporous condition increasing conductivity between the anode and cathode, and a perforate diffusing member spaced between anode and cathode assisting in vaporizing the element and diffusing the vapor of the element throughout the chamber.

2. In a spark plug for internal combustion engines, an insulated core provided with an internal chamber an anode at one end of the chamber and a cathode at the other end each spaced from the other, the anode connecting to an ignition circuit, a discharge point terminating the cathode, a medium in the chamber changeable in the presence of electric discharges to a vaporous state increasing conductivity between anode and cathode, and a screen member between anode and cathode operating as an intermediate electrode and diffuse the aforesaid vapor.

3. In a spark. plug for internal combustion engines, an insulated core provided with an internal chamber, windows permitting the inspection of the chamber from the exterior, an anode at one end of the chamber and a cathode at the other end each spaced from the other, the anode connecting to an ignition circuit, a discharge point terminating the cathode, a modicum of mercury in the chamber changeable in the presence of electric discharges to a vaporous state increasing conductivity between anode and cathode, and a screen member between anode and cathode and spaced from each operating as an intermediate electrode and diffusing the aforesaid mercury throughout the chamber when it is in a vaporous state. 7

4. A spark plug for internal combustion engines, comprising a core of insulative material provided with an internal chamber, an anode at one end of the chamber and a cathode at the other end and each spaced from the other, the anode connecting to an ignition circuit, a discharge point terminating the cathode, and a modicum of mercury in the chamber which becomes transformed in the presence of electric discharges between anode and cathode into a medium'having high conductivity and thereby reducing the resistance occasioned by the space existing between anode and cathode to the passage of electric current from the one to the other.

5. A spark plug core having an internal spark gap Whose dielectric properties are decreased by an element sealed within such core which element after an interval of electrical discharges becomes converted into a vapor having less dielectric qualities than the gap,

JOHN H. DOAK. 

